Earthquakes In North America

It is believed that this volcanic area was caused by a localised hot spot within the Pacific plate. A concentration of radioactive elements inside of the mantle may have caused this hot spot to develop. The hot spot is stationary so as the Pacific plate moves over it a line of volcanoes are made. This is more proof that the Earth’s crust is moving as suggested by Wegener.

Earthquakes can be created on any of the plate boundaries. Earthquakes occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur. The point inside the crust where the pressure is released is called the focus. The point on the Earth's surface above the focus is called the epicentre. Earthquake energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away. The most severe damage caused by an earthquake will happen close to the epicentre.

In conclusion the recent conception and development of plate tectonic theory has greatly aided our understanding of the distribution of seismic events. We now understand that there is a correlation between earthquakes/volcanoes locations and their proximity to a plate boundary plates are continually moving and earthquakes and volcanoes are found along these boundaries. Exceptions to this rule such as Hawaii also help prove tectonic theory due to their unique creation. Whilst this has helped our understanding we also recognise the fact those in LEDCs with poor access to education are unaware of plate tectonic theory so they cannot understand the hazards that some countries face, nor have the means to mitigate against them thus worsening the

The theory of plate tectonics states that Earth’s outer shell is divided into plates. The crust and upper mantle is broken into plates that move around on the mantle, changing in size throughout time. The lithosphere makes up the crust and upper mantle and the asthenosphere a plastic like layer beneath the lithosphere. There are three types of plate boundaries. Divergent boundaries where two plates move away from each other. The ocean widens and new crust forms at the mid-oceanic ridge. Convergent boundaries has three types of converging, moving two plates towards each other. First we have an ocean floor plate that collides with a less dense continental plate. Next an ocean floor plate collides with another ocean floor plate. Finally a continental plate collides with another continental plate. Transform boundaries were two plates slide past one another. The resulting effects of plate tectonics is landforms such as rift valleys,

• This earthquake may not have released all of the strain stored in its rocks next to the fault this reveals a potential earthquake in the Santa Cruz Mountains in the near future. The occurrence of the earthquake showed that the Earth did not exhaust all its strain and hence other earthquakes could be expected. However, the dates could not be predicted. The extent of the damage could have been much more devastating for the region, but with the earthquake occurring near the coast this made half of the felt area westward in the Pacific Ocean. The occurrence of aftershocks ten days later reinforces the unpredictability nature and hence makes Geology to be a study that is always evolving. In conclusion, the Earth and the study of cannot be exhausted as every natural occurrence provides a new puzzle to be solved.

The 1906 San Francisco Earthquake tectonic setting was in the outermost shell of earth known as the crust this is composed of rigid plates that have been moving for hundreds of millions of years. Two of these moving plates meet in western California; the boundary between them is a zone of faults, the principal one being the San Andreas fault. The horizontal sliding of the Pacific Plate relative to the North American Plate, causes earthquakes along the San Andreas fault and similar plates near the region. The San Andreas fault is a transform plate boundary, accommodating horizontal relative motions (usgs.gov).

The right figure gives a more specific visualization of the Juan de Fuca plate currently been forced to slip under the North American plate in an area known as the Cascadia Subduction Zone. Along the boundary of these two plates, a section has become locked yet they are still moving toward each other. As a result, stress has accumulated for centuries and when that stress relieved, it will cause the largest and most powerful earthquake called a megathrust earthquake of magnitude 9.0 or higher. The last earthquake which was caused by the relieved of this stress with similar magnitude happened in 1700. The scientists were able to determine this date through sediment samples that indicated the coast’s seismic past, taken from the sea floor off the coast of Vancouver Island. Therefore, scientist were able to outline that earthquakes occur every 500 to 1000 years.The risk for a possible megathrust earthquake to happen is increasing and it is coming faster than predicted because the stress hasn’t been released recently and the Juan de Fuca and the North American Plates are constantly moving. Right now, Vancouver Island has been tilted higher and squeezed by a few centimetres eastward every year. In the next 50 years, when the strain released, an earthquake called the “Big One” will rip down the west coast from British Columbia to northern California,

By definition an earthquake is the tremor of the surface of the Earth, sometimes severe and devastating, which results from shock waves generated by the movement of rock masses deep within the Earth, particularly near boundaries of tectonic plates. The tectonic plates involved in the 2010 Chile earthquake were the Nazca and South American plate, and like all tectonic plates, they often move due to convection currents within the Earth’s mantle. This movement can cause tectonic plates to collide, separate or slide past one another. For thousands of years, the oceanic Nazca plate has been colliding and slowly subducting underneath the continental side of the South American plate. Earthquakes can be caused by a variety of reasons, but the 2010 Chilean earthquake was caused by these two tectonic plates having an ocean-continental collision at a convergent boundary.

The New Madrid Seismic Zone is also known as the New Madrid Fault Line. A fault is a thin zone of crushed rock that separates the Earth’s crust. Whenever an earthquake takes place, it occurs on one of the faults. Then the rock on one of the sides slips with respect to the other. The fault line is made up of reactivated faults. The reactivated faults formed when North America began to separate. Faults were formed next to rift and igneous rocks were formed from the magma that was pushed up to the surface (Wapedia (2010). The rift was covered with younger sediments. The sediments that covered the rift included Mesozoic and Cenozoic sedimentary rocks of the Mississippi embayment. Large amounts of the sediment was loosely consolidated, soft and sandy as a result of the ground shaking, ground deformation, slides, slumps, and liquefaction. A mass of intrusive igneous rock (also known as pluton, mass of igneous rock and a deep reservoir of magma)

Large magnitude earthquakes occur on plate boundaries and they can produce hazards such as movement along faults, landslides, and tsunamis if the earthquake occurs close to a large enough body of water. In North America, the western coast is an active margin, meaning that it is home to earthquakes and volcanoes, a physical manifestation of the plate activity occuring. On November 3rd, 2002, in South-Central Alaska, a 7.9 magnitude earthquake ruptured along three faults; the Susinta Glacier, Denali, and Totschunda faults (Eberhart-Phillips et al., 2003). The seismic hazards associated with this event included a few large aftershocks and liquefaction, which is when saturated soil losses its strength and behaves like a liquid

The most common cause of earthquakes is movement along faults. Earth’s crust is divided into tectonic plates, which grind past each other at fault boundaries. As tectonic plates move,

“I felt very at home in California, but the place is prone to earthquakes, and the one in 1944 scared the life out of me. For months afterwards, I felt that every time I sat down, I should have to put on a seatbelt.” Earthquakes are when tectonic plates slip past each other causing a “snap’. The ground shakes violently and can even crack. Though the occurrence of an earthquake is dreadful, familiarizing yourself with the causes and effects can be useful, and in turn make it less scary.

The United States seems to focus mainly on hurricanes, rather than on earthquakes, solely for the reason that, especially recently, hurricanes have caused havoc among the citizens of America. Because of the fear that America holds towards hurricanes they are so focused

Earthquakes cause ground shaking events caused by rapid movement of falts pushing past each other. Falts, hypocenters, and epicenters are all related due to earthquakes. Falts are breaks in a rock mass that fit together perfectly with massive amounts of pressure on eachother. Most falts are locked except for very brief moments causeing earthquakes. Understanding where the earthquake originated is nessasary in messureing the scale or magnitude of the earth quake. The Hypocenter or focus is where the falts started pushing past or against eachother. The point on earths surface directly above the hypocenters is the epocenter.

     Most of the worst earthquakes are associated with changes in the shape of the Earth's outermost shell, particularly the crust. These so called tectonic earthquakes are generated by the rapid release of strain energy that is stored within the rocks of the crust, which on continents is about 22 miles thick. A small proportion of earthquakes are associated with human activity. Dynamite or atomic explosions, for example, can sometimes cause mild quakes. The injection of liquid wastes deep into the Earth and the pressures